The present invention relates to a vibration sensor of a type using a piezoelectric element and which is used, for example, to sense the knocking or vibration of an internal combustion engine.
In this type of vibration sensor, it is necessary to provide a resistor in parallel with the piezoelectric element in order to reduce the amount of thermally generated noise when the piezoelectric element is rapidly heated and cooled and to cope with disconnection failures involving the leads of the element. Such an arrangement is shown schematically in FIG. 1.
In the conventional vibration sensor of this type, the resistor has been provided outside the casing of the piezoelectric element. This has the drawback of additional wiring steps and the possibility of failure due to the breakage of the resistor or the cutting of its circuit leads.